/*
 * Copyright 2002-2012 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.core;

import java.io.Serializable;
import java.util.LinkedHashMap;
import java.util.Map;

import org.springframework.util.Assert;

/**
 * Support class for {@link AttributeAccessor AttributeAccessors}, providing
 * a base implementation of all methods. To be extended by subclasses.
 *
 * <p>{@link Serializable} if subclasses and all attribute values are {@link Serializable}.
 *
 * 属性访问器支持类
 *
 * @author Rob Harrop
 * @author Juergen Hoeller
 * @since 2.0
 */
@SuppressWarnings("serial")
public abstract class AttributeAccessorSupport implements AttributeAccessor, Serializable {

    /**
     * Map with String keys and Object values
     *
     * 属性值表
     */
    private final Map<String, Object> attributes = new LinkedHashMap<String, Object>(0);


    /**
     * 设置属性值
     *
     * @param name the unique attribute key
     * @param value the attribute value to be attached
     */
    public void setAttribute(String name, Object value) {
        Assert.notNull(name, "Name must not be null");
        if (value != null) {
            this.attributes.put(name, value);
        } else {
            removeAttribute(name);
        }
    }

    /**
     * 获取属性值
     *
     * @param name the unique attribute key
     * @return
     */
    public Object getAttribute(String name) {
        Assert.notNull(name, "Name must not be null");
        return this.attributes.get(name);
    }

    /**
     * 移除特定属性
     *
     * @param name the unique attribute key
     * @return
     */
    public Object removeAttribute(String name) {
        Assert.notNull(name, "Name must not be null");
        return this.attributes.remove(name);
    }

    /**
     * 判断某个属性是否存在
     *
     * @param name the unique attribute key
     * @return
     */
    public boolean hasAttribute(String name) {
        Assert.notNull(name, "Name must not be null");
        return this.attributes.containsKey(name);
    }

    /**
     * 获取所有属性
     *
     * @return
     */
    public String[] attributeNames() {
        return this.attributes.keySet().toArray(new String[this.attributes.size()]);
    }


    /**
     * Copy the attributes from the supplied AttributeAccessor to this accessor.
     *
     * 拷贝属性
     *
     * @param source the AttributeAccessor to copy from
     */
    protected void copyAttributesFrom(AttributeAccessor source) {
        Assert.notNull(source, "Source must not be null");
        String[] attributeNames = source.attributeNames();
        for (String attributeName : attributeNames) {
            setAttribute(attributeName, source.getAttribute(attributeName));
        }
    }


    /**
     * 判断是否相等
     *
     * @param other
     * @return
     */
    @Override
    public boolean equals(Object other) {
        if (this == other) {
            return true;
        }
        if (!(other instanceof AttributeAccessorSupport)) {
            return false;
        }
        AttributeAccessorSupport that = (AttributeAccessorSupport) other;
        return this.attributes.equals(that.attributes);
    }


    /**
     * 哈希值
     * 这里使用的是属性表的哈希值
     *
     * @return
     */
    @Override
    public int hashCode() {
        return this.attributes.hashCode();
    }

}
